Cryptococcosis is a life-threatening disease caused by the ubiquitous, eukaryotic organism, Cryptococcus neoformans. With the greater use of immunosuppressive drugs and the AIDS epidemic, there is a growing number of individuals suffering from cryptococcosis. Both human and animal studies, clearly document that the cell-mediated immune (CMI) response is the major protective host defense against this encapsulated yeast-like organism. The CMI response is a complex cascade of biological events involving numerous leukocytes, cytokines, and chemokines (chemoattractant cytokines), and when appropriately orchestrated, the CMI components eliminate cryptococci from tissues. Although it is evident that T lymphocytes functioning in the CMI response are important in protection against cryptococci, the mechanisms by which the T cells exert their activity have not been completely elucidated. Both CD4 and CD8 subsets of T cells contribute to protection; however, CD4 cells have a greater impact. The major long-term goal of this project is to gain an understanding of the sequence of biological events and factors that influence clearance of cryptococci, so that measures can be devised to reestablish a protective pathway in immunodeficient individuals through immunoreplacement or immunomodulatory therapeutic procedures. We propose to focus attention on understanding the details of the expression phase of the anticryptococcal CMI response, because it is through this phase of the response that the organism is eliminated. Recently we have developed a means of eliciting a CMI reaction to cryptococcal antigen (CneF) in a gelatin sponge matrix implanted into the backs of immune mice. This procedure allows us to retrieve and examine the fluid and cells from the reaction site. Thus far, we have defined the kinetics of cellular infiltrates into the CMI-reactive sponges and established that TNF, IL-2, IFNgamma, and IL-5 are produced as a part of the reaction. In this application, we propose to use the gelatin sponge model to further define the cells, cytokines, and chemokines and their function in clearance of C. neoformans from immune and naive mice. Experiments will be done to test ways of modulating the response to achieve greater protective capacity. Finally, we will determine if the factors (cells, cytokines, and chemokines) associated with limited growth of cryptococci in the sponges are also functional in infected tissues such as lung, spleen, liver, and - brain. Findings from the proposed studies with CneF immunization and cryptococcal infection models, along with appropriate controls, should provide the necessary knowledge to devise effective vaccines or immunotherapy against C. neoformans.